Synthesis Of Chiral Liquid Crystals Based On Borneol

Chiral liquid crystals have attracted more and more attention at present.Molecular chirality has a particularly remarkable influence on the macroscopic physical properties of liquid crystal systems.Many physical properties of liquid crystals depend on chirality,e.g.,certain linear and nonlinear optical properties,the occurrence of ferro-,ferri-,antiferro-and piezo-electric behavior,the electroclinic effect,and even the appearance of new phases.In addition,the majority of optical applications of liquid crystals is due to chiral structures,namely the ther-mochromic effect of cholesteric liquid crystals,the rotation of the plane of polarization in twisted nematic liquid crystal displays,and the ferroelectric and antiferroelectric switching of smectic liquid crystals.In this thesis,we synthesized a series of chiral liquid crystal compounds and side chain liquid crystalline polymers containing borneol,and their structures and liquid crystal behaviors were identified.This thesis is divided into three parts.In the first part,we synthesized a series of chiral liquid crystal compounds,(BnEB:B4EB,B5EB,B6EB,B7EB,B8EB,B9EB,B10EB),using borneol group as chiral primitives,-/-ArCOOAr-Ar-/-as the rigid mesogenic core,ethoxy group as the terminal group.The effect of the length of dicarboxylic acid spacer on liquid crystal properties was discussed.During the heating process,liquid crystal compounds B4EB,B5EB,B6EB,B7EB and B8EB present oily streak texture,B9EB and B10EB show oily streak texture and fan-shaped texture.During the cooling process,the compound B4EB shows focal conic texture.The compound B5EB shows focal conic texture,fingerprint texture and pseudo-isotropic pattern.B6EB,B8EB and B10EB present focal conic,filament pattern,pseudo-isotropic pattern and chiral smectic C phase.B7EB and B9EB reveal focal conic texture,schlieren texture and pseudo-isotropic pattern.In the second part,we synthesized a series of chiral liquid crystal compounds,using borneol group as chiral primitives,-/-ArCOOAr-Ar-/-as the rigid mesogenic core,adipic acid acting as space group,alkoxy group as the terminal group.The effect of the length of alkoxy group on liquid crystal properties was discussed.Compound BOB2B presents oily streak texture during the heating process.BOBnB(n=4,6,8,10,12)show SC*phase and oily streak texture.BOBnB(n=14,16,18)show SC*phase.During the cooling process BOB2B shows focal conic texture,BOB4B,BOB6B and BOB8B present focal conic texture,filament pattern,pseudo-isotropic pattern and chiral smectic C phase.BOB 1 OB and BOB12B reveal focal conic and fingerprint texture.BOB14B3 BOB16B and BOB18B show fingerprint texture.In the third part,we synthesized a series of chiral liquid crystal monomers(BmBAB:B4BAB,B6BAB,B8BAB,B10BAB,B12BAB)using borneol group as chiral primitives,a reactive alkene group as end group,A series of P1?P5 polymers were prepared by graft polymerization using silicone oil as backbone.During the heating process,B4BAB presents oily streak texture;B6BAB,B8BAB and B12BAB present chiral smectic C phase and oily streak texture;B10BAB shows chiral smectic X phase,chiral smectic C phase and oily streak texture.And during the cooling process,B4BAB and B12BAB show focal conic texture and chiral smectic C phase;BmBAB(m=6,8,10)present focal conic texture,pseudo-isotropic pattern,chiral smectic C phase and chiral smectic X phase.A series of P1?P5 polymers were prepared by graft polymerization using PMHS as backbone.P1-P5 show that this series of polymers present iridescent texture in the liquid crystal range.Polymers P1?P5 are identified as chiral smectic A liquid crystal by POM and XRD.